Businesses which have adopted wireless LANs transmit data using wireless technologies such as, but not limited to radio frequency (RF) and/or infrared (IR) transmissions. FIG. 1 illustrates a typical packet transmission system comprising a wireless LAN 100. For the purpose of this discussion, wireless LAN 100 includes a system access point (AP) 120 which utilizes RF communications to communicate with a plurality of user devices (UDs) 110 such as portable computers, lap-top computers, personal digital assistants (PDAs) and the like. AP 120 is connected to data network 130 by channel 132 which may include, but is not limited to wires or optical links.
AP 120 controls communication within the illustrated network by passing information to and from data network 130 and the plurality of devices 110. Individual devices 110 are capable of direct communications without assistance by AP 120. Data network 130 may consist of an Ethernet network, a Token Ring network or any other of the well known data networks.
In the system of FIG. 1, problems with data delivery begin to surface as the distance between communicating devices increases. Because devices 110 are capable of independent communications, two such devices may lose communications if they venture outside of their respective ranges of radio coverage. A similar situation arises when devices 110 employ power management schemes which permit the devices to operate in either an active or a sleep mode of operation. As will be appreciated, when a device 110 enters the sleep mode of operation, only the basic device functions such as system clock, timers, interrupts, etc. are operational. During the sleep mode, power to the rest of the device hardware is turned off. In particular, the wireless transceiver portion of an asleep device 110 receives no power, thus, the device can neither transmit or receive information, and therefore cannot perform any communications activities.
Under the above scenarios, the channel access performance of an asleep device or between two devices that are out of range of each other is severely impaired due to their inability to communicate. It would be extremely advantageous therefore to provide a method for assuring packet delivery in a wireless LAN that improves the channel access performance of asleep and/or out-of-range devices.